1. Field of the Invention
The present invention relates to a test pin unit to be used in test apparatus for carrying out a test on a subject to evaluate electric characteristics of the subject such as a semiconductor wafer or an electric circuit board of an electrical appliance.
2. Description of the Prior Art
Heretofore, test apparatus designed specifically for individual subjects such as semiconductor wafers and electric circuit boards of electrical appliances have been used for carrying out tests on these subjects to evaluate their electric characteristics, respectively. Generally, each test apparatus comprises a plurality of test pin units and a substrate. The pin unit has a test pin to be brought into contact with a predetermined test point (pad) of the subject. Such a conventional test pin is provided as a combination with a spring or the like wound around the test pin. Therefore, the test pin is spring-loaded by a spring tension. In addition, the substrate has a plurality of pores. Each of the test pin units is inserted into the pore. Furthermore each of the test pin units is connected to a lead wire.
For testing the electric characteristics of the subject, each of the test pins of the test apparatus is brought into contact with a test point of the subject. Then, the test apparatus is pressed against the subject while maintaining the contact between the test pin and the test point. In this case, the test pin can be in contact with the test point as the spring tension exerts a certain stylus force thereon. Subsequently, a certain electric signal is sent to each test pin through the lead wire to carry out a test on the subject to evaluate electric characteristics of the subject.
The tip of the test pin becomes deformed as the number of usages of the test pin increases. At the time of carrying out the test, therefore, there is a possibility of causing several problems such as the increase in contact resistance of the test pin to the test point of the subject and the generation of contact failure of the test pin to the test point of the subject. If one of such problems arises, there is a need to replace a wornout test pin with a new one. In this case, however, it is difficult to replace only the worn-out test pin with a new one because the conventional test pin is integrally constructed with a spring member. In other words, the whole of the test pin unit having the worn-out test pin should be junked and should be replaced with a new test pin unit. Consequently, the conventional test pin has a disadvantage of mounting costs at the time of test-pin replacement.
The present invention has been completed in view of the above disadvantage of the conventional test pin. Therefore, an object of the present invention is to provide a test pin unit that allows a test-pin replacement at a substantially low cost, compared with the conventional one.
For attaining the above object, there is provided a test pin unit to be used in a test apparatus for carrying out a test on a subject to evaluate electric characteristics of the subject such as a semiconductor wafer or an electric circuit board of an electrical appliance, having a test pin to be brought into contact with a predetermined test point on the subject, comprising: a movable member capable of moving within a predetermined distance along a predetermined reference axis; means for forcing the movable member toward the distal end of the predetermined reference axis; and a retaining member for retaining the test pin substantially parallel to the reference axis in a removable manner, where the retaining member is integrally mounted on the movable member.
Here, the retaining member may preferably comprise a housing part for housing a part of the test pin and at least one screw provided on the periphery of the housing part, where the test pin is fixed on the housing part by housing the part of the test pin and then securing the part of the test pin on the housing part by the screw.